Imlunestrant plus abemaciclib cleared for ESR1-mutated advanced breast cancer

What this means

Breast cancer that is estrogen receptor-positive (ER+) and HER2-negative accounts for the majority of advanced breast cancers, and most patients receive endocrine therapy (drugs that lower or block estrogen). Over time, some of these tumors acquire a mutation in the ESR1 gene that changes the shape of the estrogen receptor so it no longer needs estrogen to keep the tumor growing — this mutation is a common driver of resistance to standard endocrine therapies. Inluriyo (imlunestrant) is Eli Lilly's oral selective estrogen receptor degrader (SERD) designed to bind and destroy both wild-type and mutant estrogen receptors. On September 18, 2026 the FDA approved Inluriyo in combination with Verzenio (abemaciclib, a CDK4/6 inhibitor also from Lilly) for adults with ER+/HER2-/ESR1-mutated advanced or metastatic breast cancer whose disease has progressed after at least one line of endocrine therapy. Eligibility requires confirming the ESR1 mutation with an FDA-authorized test — the Guardant360 CDx (Guardant Health) was approved as the companion diagnostic the same day. In the Phase 3 EMBER-3 trial, the imlunestrant + abemaciclib combination doubled median progression-free survival compared with imlunestrant alone (11.1 months vs 5.5 months) and roughly tripled the objective response rate (35% vs 15%) in patients whose tumors carried the ESR1 mutation. This is the first-ever FDA approval of imlunestrant.